Depression and comorbid cognitive impairment in the elderly can be difficult to distinguish from dementia. Adding to the complex differential is that depression may be part of a bipolar illness rather than a unipolar mood disorder. A diligent workup and close monitoring of patients can inform appropriate treatment and can make the difference between recovery and persistence of symptoms. The present case will illustrate how a comprehensive workup utilizing extensive data gathering, laboratory workup, use of neuropsychological testing, neuroimaging, and timely treatment can lead to successful clinical outcomes that can be sustained for many years.